Chair backrest



FIG. 1 is a front perspective view of the chair backrest of the present design as part of a theater style chair;

FIG. 2 is a front elevation view of the chair backrest of the present design;

FIG. 3 is a back elevation view of the chair backrest of the present design;

FIG. 4 is a side elevation view of the chair backrest of the present design, the opposite side view being a mirror image thereof;

FIG. 5 is a front, top perspective view of the chair backrest of the present design; and,

FIG. 6 is a front, bottom plan view of the chair backrest of the present design, the chair backrest rotated upside down.

The broken lines and the dashed lines form no part of the claimed design. 

CLAIM The ornamental design for a chair backrest, as shown and described. 